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The circular economy is considered as an alternative model to the unsustainable linear “take–make–waste” approach that characterizes contemporary economic systems. It aims to achieve sustainable development by promoting the responsible and cyclical use of resources to maintain their value in the economy and minimize pressures on the environment. Biochar systems offer opportunities for operationalizing the CE model. They are multifunctional systems that can be used for bioenergy and biochar production using an extensive range of biomass feedstocks, including biowaste. They can contribute to climate change mitigation, as producing biochar and mixing it with soil is a means for sequestering atmospheric CO2. Moreover, the produced biochar has a wide range of applications, including its use for agricultural soil amendment, wastewater treatment, manufacturing of cement, and remediation of contaminated soils. This versatility of biochar systems creates great opportunities for developing circular models of waste management that can valorize different waste streams. This chapter provides an overview of the CE concept and describes biochar systems, focusing on systems for the synergistic valorization of wood waste and contaminated soils. It also discusses the role of these systems in the CE indicating that they can contribute to the transition toward the CE.

The blooming of beach-cast seaweed has caused environmental degradation in some coastal regions. Therefore, a proper treating and utilizing method of beach-cast seaweed is demanded. This study investigated the potential of producing power or biofuel from pyrolysis of beach-cast seaweed and the effect of the ash-washing process. First, the raw and washed beach-cast seaweeds (RS and WS) were prepared. Thereafter, thermogravimetric analysis (TG), bench-scale pyrolysis experiment, process simulation, and life cycle assessment (LCA) were conducted. The TG results showed that the activation energies of thermal decomposition of the main organic contents of RS and WS were 44.23 and 58.45 kJ/mol, respectively. Three peak temperatures of 400, 500, and 600 °C were used in the bench-scale pyrolysis experiments of WS. The 600 °C case yielded the most desirable gas and liquid products. The bench-scale pyrolysis experiment of RS was conducted at 600 °C as well. Also, an LCA was conducted based on the simulation result of 600 °C pyrolysis of WS. The further process simulation and LCA results show that compare to producing liquid biofuel and syngas, a process designed for electricity production is most favored. It was estimated that treating 1 ton of dry WS can result in a negative cumulative energy demand of -2.98 GJ and carbon emissions of -790.89 kg CO

The biochar-agriculture nexus can potentially generate several benefits ranging from soil carbon sequestration to the reduction in nutrient leaching from arable soils. However, leveraging these benefits requires spatially-explicit information on suitable locations for biochar application. This study provides a flexible multicriteria framework that delivers spatial indications on biochar prioritization through a biochar use indication map (BUIM). The framework was exemplified as a case study for Swedish arable land through three different prioritization narratives. The BUIM for all the narratives revealed that a significant fraction of the Swedish arable land could potentially benefit from biochar application. Furthermore, arable land that scored high for a given narrative did not necessarily score high in the others, thus indicating that biochar application schemes can be adjusted to various objectives and local needs. The framework presented here aims to promote the exploration of different avenues for deploying biochar in the agricultural sector.

Concerns over climate change have led to the promotion of biofuels for transport, particularly biodiesel from oilseed crops and ethanol from sugar and starch crops. However, the climate-change mitigation potential of the various biofuels estimated in published studies tends to vary significantly, questioning the reliability of the methods used to quantify potential impacts. We investigated the values published in the European Commission's Renewable Energy Directive (RED), and recalculated the climate-change impacts of a range of biofuels using internally-consistent attributional and consequential modelling approaches to enable comparison of these approaches. We conclude that the estimated results are highly dependent on the modelling approach adopted, to the detriment of the perception of the robustness of life cycle assessment as a tool for estimating the climate-change impacts of biofuels. Land use change emissions are a determining parameter which should not be omitted, even if modelling it introduces a large variability in the results and makes interpretation complex. Clearer guidelines and standardization efforts would be helpful in the harmonization of LCA practice, so that the results can be more useful, robust and reproducible. Made available in DSpace on 2021-12-29T12:02:21Z (GMT). No. of bitstreams: 1 Novaes-Modelling-approach-2021.pdf: 1349270 bytes, checksum: 438172d29aab63075adfda6a22332140 (MD5) Previous issue date: 1

The use of biochar to stabilize soil contaminants is emerging as a technique for remediation of contaminated soils. In this study, an environmental assessment of systems where biochar produced from wood waste with energy recovery is used for remediation of soils contaminated with polycyclic aromatic hydrocarbons (PAH) and metal(loid)s was performed. Two soil remediation options with biochar (on-and off-site) are considered and compared to landfilling. The assessment combined material and energy flow analysis (MEFA), life cycle assess-ment (LCA), and substance flow analysis (SFA). The MEFA indicated that on-site remediation can save fuel and backfill material compared to off-site remediation and landfilling. However, the net energy production by pyrol-ysis of wood waste for biochar production is 38% lower than incineration. The LCA showed that both on-site and off-site remediation with biochar performed better than landfilling in 10 of the 12 environmental impact catego-ries, with on-site remediation performing best. Remediation with biochar provided substantial reductions in cli-mate change impact in the studied context, owing to biochar carbon sequestration being up to 4.5 times larger than direct greenhouse gas emissions from the systems. The two biochar systems showed increased impacts only in ionizing radiation and fossils because of increased electricity consumption for biochar production. They also resulted in increased biomass demand to maintain energy production. The SFA indicated that leaching of PAH from the remediated soil was lower than from landfilled soil. For metal(loid)s, no straightforward conclusion could be made, as biochar had different effects on their leaching and for some elements the results were sensitive to water infiltration assumptions. Hence, the reuse of biocharremediated soils requires further evaluation, with site-specific information. Overall, in Sweden's current context, the biochar remediation technique is an environmentally promising alternative to landfilling worth investigating further.(c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

Biochar has been recognised as a carbon dioxide removal (CDR) technology. Unlike other CDR technologies, biochar is expected to deliver various valuable effects in e.g. agriculture, animal husbandry, industrial processes, remediation activities and waste management. The diversity of biochar side effects to CDR makes the systematic environmental assessment of biochar projects challenging, and to date, there is no common framework for evaluating them. Our aim is to bridge the methodology gap for evaluating biochar systems from a life-cycle perspective. Using life cycle theory, actual biochar projects, and reviews of biochar research, we propose a general description of biochar systems, an overview of biochar effects, and an evaluation framework for biochar effects. The evaluation framework was applied to a case study, the Stockholm Biochar Project. In the framework, biochar effects are classified according to life cycle stage and life cycle effect type; and the biochar's end-of-life and the reference situations are made explicit. Three types of effects are easily included in life cycle theory: changes in biosphere exchanges, technosphere inputs, and technosphere outputs. For other effects, analysing the cause-effect chain may be helpful. Several biochar effects in agroecosystems can be modelled as future productivity increases against a reference situation. In practice, the complexity of agroecosystems can be bypassed by using empirical models. Existing biochar life cycle studies are often limited to carbon footprint calculations and quantify a limited amount of biochar effects, mainly carbon sequestration, energy displacements and fertiliser-related emissions. The methodological development in this study can be of benefit to the biochar and CDR research communities, as well as decision-makers in biochar practice and policy.

Several cities in Sweden are aiming for climate neutrality within a few decades and for negative emissions thereafter. Combined biochar, heat, and power production is an option to achieve carbon sequestration for cities relying on biomass-fuelled district heating, while biochar use could mitigate environmental pollution and greenhouse gas emissions from the agricultural sector. By using prospective life cycle assessment, the climate impact of the pyrolysis of woodchips in Stockholm is compared with two reference scenarios based on woodchip combustion. The pyrolysis of woodchips produces heat and power for the city of Stockholm, and biochar whose potential use as a feed and manure additive on Swedish dairy farms is explored. The climate change mitigation trade-off between bioenergy production and biochar carbon sequestration in Stockholm's context is dominated by the fate of marginal power. If decarbonisation of power is achieved, building a new pyrolysis plant becomes a better climate option than conventional combustion. Effects of cascading biochar use in animal husbandry are uncertain but could provide 10-20% more mitigation than direct biochar soil incorporation. These results help design regional biochar systems that combine negative carbon dioxide emissions with increased methane and nitrous oxide mitigation efforts and can also guide the development of minimum performance criteria for biochar products.

Several small-scale pyrolysis plants have been installed on Swedish farms and uptake is increasing in the Nordic countries. Pyrolysis plants convert biomass to biochar for agricultural applications and syngas for heating applications. These projects are driven by ambitions of achieving carbon dioxide removal, reducing environmental impacts, and improving farm finances and resilience. Before policy support for on-farm pyrolysis projects is implemented, a comprehensive environmental evaluation of these systems is needed. Here, a model was developed to jointly: (i) simulate operation of on-farm energy systems equipped with pyrolysis units; (ii) estimate biochar production potential and its variability under different energy demand situations and designs; and (iii) calculate life cycle environmental impacts. The model was applied to a case study farm in Sweden. The farm's heating system achieved net carbon dioxide removal through biochar carbon sequestration, but increased its impact in several other environmental categories, mainly due to increased biomass throughput. Proper dimensioning of heat constrained systems is key to ensure optimal biochar production, as biochar production potential of the case farm was reduced under expected climate change in Sweden. To improve the environmental footprint of future biochar systems, it is crucial that expected co-benefits from biochar use in agriculture are realised. The model developed here is available for application to other cases. (c) 2020 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).